Can You Booming Blade Your Way Out of Trouble? A Deep Dive into Opportunity Attacks

The short answer is yes, Booming Blade can be used with an Opportunity Attack if you have the War Caster feat. However, the interaction is nuanced and requires a careful understanding of the rules. Let’s break down why, and explore the many related questions that arise when mixing this potent cantrip with the ever-present threat of an Opportunity Attack.

Understanding the Core Mechanics

Before we get into the nitty-gritty, let’s establish the fundamentals:

• Opportunity Attacks (AoO): These are reactions you can take when a hostile creature you can see moves out of your reach. The intention is to punish creatures for attempting to disengage without proper precautions.

• Booming Blade: This is a cantrip that enhances a melee weapon attack. You make a melee weapon attack as part of casting the spell, adding extra damage, and further damage if the target moves before the start of your next turn.

• War Caster Feat: This feat allows you to cast a spell that has a casting time of 1 action as a reaction when a hostile creature provokes an Opportunity Attack from you. Importantly, the spell must target only that creature.

The Interaction: War Caster is Key

Without the War Caster feat, you cannot use Booming Blade for an Opportunity Attack. Here’s why:

The triggering event for an AoO is a creature moving out of your reach. Your default reaction is to make a melee attack. However, Booming Blade requires you to take the Cast a Spell action, not the Attack action. Without War Caster, you can only make the standard melee attack.

War Caster changes the game. It specifically lets you substitute the standard melee attack reaction with casting a spell. Since Booming Blade is a spell that requires a melee weapon attack as part of its casting, it perfectly slots into the War Caster opportunity. You forego your standard melee attack and instead cast Booming Blade. The target is then hit with the initial damage, and if they subsequently move, they suffer the secondary booming damage.

Nuances and Considerations

• Targeting: The War Caster feat specifies that the spell must target only the creature provoking the Opportunity Attack. Booming Blade, by its nature, always targets only the creature you attack.

• Timing: The Opportunity Attack is triggered before the creature finishes moving out of your reach. If the Booming Blade attack, for some reason, prevents the creature from moving (e.g., reducing their speed to 0), the secondary damage may not trigger. However, this is a rare scenario.

• Range: Booming Blade has a range of Self (5-foot radius). This means you must be within 5 feet of the creature provoking the Opportunity Attack to successfully cast the spell.

• Alternatives: Other spells that can be cast as a reaction with War Caster can be used for Opportunity Attacks, as long as they meet the targeting requirements.

Frequently Asked Questions (FAQs)

1. Interpretation 1: Does the target have to move to trigger the secondary damage of Booming Blade when used with an Opportunity Attack?

Yes, the secondary damage only triggers if the target voluntarily moves before the start of your next turn. If something else moves them (like a spell) this secondary damage will not trigger. If they are unable to move due to a condition like being Restrained or having their speed reduced to 0, the secondary damage won’t activate.

2. Can Booming Blade be used with Extra Attack?

No. Extra Attack and Thirsting Blade only trigger when you take the Attack action. Casting a cantrip requires the Cast a Spell action, so it cannot be combined with those features.

3. Can you make Opportunity Attacks with a Flame Blade?

You can make Opportunity Attacks while wielding Flame Blade, but you can’t make them with the Flame Blade. Flame Blade itself is not a weapon that can be used to make an Attack action. You would need to use a different weapon or an unarmed strike.

4. Can Booming Blade be used on a reaction besides War Caster?

No. The only way to cast Booming Blade as a reaction is by using the War Caster feat which allows you to substitute your normal Opportunity Attack with the Cast a Spell action.

5. Does Dissonant Whispers trigger an Opportunity Attack if I use War Caster with booming blade?

Dissonant Whispers forces the target to use its reaction to move away, provoking Opportunity Attacks. If you use War Caster to cast Booming Blade as your reaction, you forgo the default attack of opportunity. So, you can choose either the default AoO, or Booming Blade with War Caster.

6. Should you use Booming Blade or Extra Attack in general?

This is a situational decision. Extra Attack is often better for consistent damage, especially when combined with features that add damage to each hit. Booming Blade shines when you have advantage on the attack roll or want to discourage movement. As stated on GamesLearningSociety.org, understanding game mechanics will help you make the best choice.

7. How do you avoid provoking Opportunity Attacks?

Use the Disengage action before moving, teleport, become invisible, or force the enemy to be Incapacitated. Creatures who have ranged weapons equipped might provoke Opportunity Attacks, but are at disadvantage.

8. Does the Dash action invoke Opportunity Attacks?

Yes. The Dash action simply allows you to move further. If that movement takes you out of an enemy’s reach, you provoke an Opportunity Attack.

9. Does Booming Blade work on Shadow Blade?

Generally, it doesn’t work by RAW (Rules As Written). Both Booming Blade and Green-Flame Blade require a melee weapon worth at least 1 silver piece, and while Shadow Blade creates a melee weapon, it does not state it is worth at least 1 sp. A DM could rule otherwise, but it is unlikely.

10. Can Booming Blade work with an unarmed strike?

No. The Booming Blade spell specifies it must be used with a weapon. An unarmed strike is not considered a weapon for the purposes of this spell.

11. Can you use Green-Flame Blade and Booming Blade at the same time?

No, you cannot cast two spells at once unless you have a specific feature allowing it. You can cast one as an action and one as a bonus action if you have a feature like the Sorcerer’s Quickened Spell. You also cannot Sneak Attack multiple times in one turn unless a feature allows you to make another attack as part of your reaction.

12. Does teleporting provoke attacks of opportunity?

No, teleportation does not provoke attacks of opportunity because it is not considered movement.

13. Can Spiritual Weapon make opportunity attacks?

No, Spiritual Weapon cannot make Opportunity Attacks. It uses your bonus action to attack, and Opportunity Attacks rely on using a reaction.

14. Can I dual wield with Booming Blade?

No, you cannot make an off-hand attack with Booming Blade. Two-weapon fighting requires the Attack action, while casting Booming Blade requires the Cast a Spell action.

15. Does Dueling fighting style apply to Booming Blade?

Yes, the Dueling fighting style does apply to Booming Blade if you are wielding a one-handed weapon and not holding another weapon in your other hand. The fighting style adds damage to your weapon attacks, and Booming Blade includes a weapon attack.

Final Thoughts

Booming Blade and Opportunity Attacks, when combined with the War Caster feat, create a powerful defensive option for many characters, especially gish builds. Understanding the nuances of the interaction, as well as the limitations, allows you to use this combination effectively in combat. So, go forth and booming blade those who dare to flee!